This invention relates generally to telephone communications apparatus and more particularly to a frequency shift keyed (FSK) trunk dialing converter for controlling two-way communications between telephone systems utilizing standard E and M lead control.
Trunk dialing converters for connecting a local telephone set to a remote telephone set over a high frequency radio link, for example, are generally known. In such applications, a trunk dialing converter is located on each side of the link to couple the telephone sets through the respective telephone systems which could include PBX apparatus. Each trunk dialing converter includes circuit means for generating FSK seizing, dialing, answering, and clearing signals which are transmitted as voice frequency tones frequency modulated about a center frequency. Also included in each converter are a pair of separate voice path circuits, one for transmitting to and one for receiving voice communications from the link which may include, for example, a "Lincompex" system. The voice paths, however, are interrupted during FSK control signal transmission and reception.
Typical examples of known prior art trunk systems are disclosed in the following patents: U.S. Pat. No. 3,261,923, entitled, "Frequency-Shift Dial Pulsing System", which issued to L. T. Anderson, et al. on July 19, 1966; U.S. Pat. No. 3,349,191, entitled, "Talk-off Protection for In-band Telephone signaling Systems, which issued to H. Mann on Oct. 24, 1967; and U.S. Pat. No. 3,790,719, entitled, "Method and Means for Connecting Branch Exchanges", which issued to B. R. Montague, et al. on Feb. 5, 1974.
Accordingly, it is an object of the present invention to provide an improvement in telephone communication apparatus.
It is a further object of the invention to provide an improvement in trunk dialing apparatus.
It is yet another further object of the invention to provide an improvement in digital trunk dialing apparatus.
And it is still a further object of the invention to provide an improvement in digital frequency shift keyed (FSK) trunk dialing apparatus.